A fundamental component of cognitive behavior involves abstracting rules and forming concepts. While research on concept formation has exclusively examined the types of abstractions that are formed during encoding, abstractions are also formed as a result of computations that are performed on retrieved rather than incoming information. Despite the pervasiveness of this form of conceptual behavior, there has been little systematic investigation of abstraction processes that operate on retrieved information. The goal of the current proposal is to develop a general framework for understanding the interaction between categorization, abstraction, and memory processes. Experiments are proposed to investigate the general characteristics and constraints associated with retrieving, re-encoded, and analyzing stored examples in the process of forming generalizations, constructing categories, and making categorization decisions. The general procedure for the experiments is to delay attempts to analyze category information until after the information has been encoded, so that abstraction processes operate on retrieved rather than incoming information. The results of the proposed experiments will contribute not only to the development of a general framework for understanding the interaction between memory and abstraction processes, but also to our understanding of several basic cognitive phenomena. Given that categorization tasks in many circumstances, including the mental health area, involve substantial input from retrieval processes, the results of these experiments will have relevance to a number of categorization processes that occur in the mental health field. Memory-based abstraction processes not only apply to patients in a therapeutic environment who retrieve and analyze prior episodes in order to categorize and form generalizations about these experiences, but also on evaluation, diagnostic, and treatment decisions made by clinicians. The proposed experiments also investigate the use of a number of decision rules and categorization processes experiments also investigate the use of a number of decision rules and categorization processes that are central to clinical diagnosis, such as sensitivity to correlations (e.g. between psychological symptoms and diagnostic categories) and the use of prototypical representations of categories (e.g., in diagnostic classification). Once the basic cognitive processes that constrain memory-based classification and decision making are understood, this knowledge can be used to enhance performance on a number of classification tasks in the mental health field, such as psychodiagnosis.